Local attorney-general Mohammad Marzieh said the 16 were hanged Saturday morning in the city of Zahedan, in Sistan and Baluchestan province, the semi-official news agency said.

"We had issued warnings previously that bandits and anti-Iran group members who commit acts causing damage to innocent people or security and military personnel will face reciprocal action by us," he is quoted as saying.

"This morning, in retaliation for the martyrdom of border guards at the town of Saravan, we hanged 16 members of of these anti-Iran groups. The judiciary will absolutely not tolerate such actions by these groups."

Official news agency IRNA said 14 Iranian border guards were killed in the clashes in the Saravan city area, near Iran's border with Pakistan's Balochistan province. Six more were injured and three taken hostage, the news agency said. It earlier said as many as 17 security personnel had died.

Ali Abdollahi, Iran's deputy interior minister, told IRNA that the provincial governor had sent a team to investigate the incident.

He told the news agency that only authorized reports by the interior ministry regarding the killing of the soldiers and border guards should be trusted.

Abdollahi said the "terrorist activities" in Saravan appeared to have initiated over the border in Pakistan. Iran expects Pakistan to do more to secure its borders in line with mutual agreements, he said.

Iran's President Hassan Rouhani urged the interior ministry to take strong measures to deal with terrorism, IRNA said.

He also called on the foreign ministry to work out a deal with Pakistan to avoid this kind of incident happening again, the news agency said.

Rouhani also expressed his condolences to the families of the border guards killed in the incident.

Additional security and military forces from elsewhere in the province have been sent to the border area, the news agency said.